1. Field of the Invention
The present invention relates to a new polyurethane and a process for preparing same. More particularly, the present invention relates to a new polyurethane containing therein a hard segment derived from at least one specific polyhydroxy substance selected from cellulosic substances, hemi-cellulosic substances and lignic substances as well as a process for preparing the polyurethane according to a method known per se wherein at least one of the above specific polyhydroxy substance is used as a part or whole of a polyhydroxy ingredient to be reacted with a polyisocyanate ingredient.
2. Description of the Prior Art
From the past, various kinds of polyurethanes derived from various polyhydroxy ingredients and various polyisocyanates are known in the field of resins and plastics. In the production of polyurethanes, the polyhydroxy reactant to be polycondensed with a polyisocyanate reactant is generally a polyol compound or a sugar which is called a soft segment component capable of forming a soft segment by the reaction with a polyisocyanate. Up to the present, however, no polyurethanes derived from lignocelluose as a hard segment component have been known in this art. In general, cellulosic substances including cellulose itself and derivatives thereof having unreacted hydroxyl groups are polymeric polyhydroxy compounds, i.e. polyhydroxy compounds having macromolecular polymer skeletons, and behave differently from monomeric polyhydroxy compounds such as saccharides. Among the cellulosic substances broadly termed, lignocellulose is contained not only in pulp as a main product in pulp industry but also in various kinds of by-products, agricultural waste materials, etc. and is now watched as a substance effective utilization of which is strongly desired.
On the other hand, chemical modifications in various resinous materials including polyurethane are continuously studied in this art to improve their useful properties.
Under the above mentioned circumstances, there is a great demand in the field of agricultural industry including pulp industry to find effective utilization of lignocellulose as chemical starting material and thereby developing a new art for improving the quality of various synthetic materials.